Two Mexican police chiefs have been killed in separate incidents in the latest wave of violence near the Mexico-U.S. border.

The body of Javier Garcia, the police chief of the town of Sabinas Hidalgo, was found outside of town hours after he was kidnapped at gunpoint Monday afternoon. He had been shot in the back of head and handcuffed.

Hours later, Hector Ayala was shot to death in an ambush as he was driving through the streets of San Pedro Garza, a wealthy town just outside Monterrey.

Rival gangs have been fighting for control of lucrative drug smuggling routes into the U.S. from northeast Mexico.

A journalist was seriously wounded last week when gunmen attacked the offices of a newspaper in the town of Nuevo Laredo.